dotnet/runtime

PipeReader.AdvanceTo throws InvalidCastException

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#849 opened on Dec 13, 2019

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 (1 comment) (0 reactions) (0 assignees)C# (5,445 forks)batch import
area-System.IO.Pipelineshelp wanted

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Description

I'm puzzled by the fact that PipeReader.AdvanceTo accepts a default(SequencePosition) but throws InvalidCastException when provided a position from an empty sequence. Is that by design?

var pipe = new Pipe();
pipe.Reader.AdvanceTo(default); // this works
pipe.Reader.AdvanceTo(ReadOnlySequence<byte>.Empty.Start); // this throws InvalidCastException

Should it throw ArgumentException instead given the SequencePosition came from an unrelated ReadOnlySequence<byte>?

I'm a bit puzzled that PipeReader.AdvanceTo can be called before reading anyway.

Contributor guide

Research direction
Inspect the implementation of PipeReader.AdvanceTo to understand why it throws InvalidCastException when given a position from an empty ReadOnlySequence, and verify if ArgumentException would be more appropriate. Check the relevant source code in dotnet/runtime.
Tech stack
csharp
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
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1-3 hours
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Active
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Clear
Prerequisites
C#
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70